Intense discussions are taking place at Westminster that could lead to the emergence of a new centrist party consisting of six or more disaffected anti-Brexit Labour MPs along with the involvement of some Conservatives and the backing of the Liberal Democrats.

Labour MPs reported that some of those involved had lobbied backbench colleagues they thought were sympathetic as to how they could “make the shift” away from a tribal loyalty to the party.

The argument put forward was that the set of values that had drawn them to the Labour party, such as European solidarity, free movement, liberalism and anti-racism, could now be found elsewhere.

Those involved in the talks say frustrations over pro-Brexit policies pursued by Jeremy Corbyn and Theresa May, coupled with Labour-specific concerns about antisemitism, have taken a handful of MPs to the point where they are seriously considering quitting.

Labour MPs at the centre of the discussions include Chris Leslie, Chuka Umunna, Angela Smith and Gavin Shuker, signalling their intention to ratchet up the pressure on Corbyn in the hope he will whip his MPs to back an amendment calling for a second referendum.

“It’s time to start to make them realise that this is existential for the leadership,” said one potential splitter.

Luciana Berger has also been seriously considering her position as a Labour MP because of her dissatisfaction at the party’s approach to Brexit and the handling of antisemitism cases.

Close friends within Labour have been trying to persuade Berger, the MP for Liverpool Wavertree, to stay over recent days. Some party colleagues say that if she were to go it could represent a tipping point.

Conservative MPs considering their futures, according to those involved in the talks, include Sarah Wollaston, the MP for Totnes, Anna Soubry, the MP for Broxtowe, and Heidi Allen, who represents South Cambridgeshire.

The three have cooperated closely with Labour MPs as part of the People’s Vote second referendum campaign, and were all lead signatories of an amendment on Thursday that forced the government to agree to release no-deal cabinet documents.

Those involved in the discussions believe that a crunch point could come at the end of February, when pro-EU Labour MPs desperately want Corbyn to back a second referendum and restless Conservatives want May to rule out no deal of she cannot get a revised Brexit agreement through parliament.

Another idea circulating is that the new group could be called the Reformist party, with the Lib Dems contributing national and local resources. “There are a lot of generals here without an army – well the Lib Dems have an army of members,” one MP involved said.

A Labour MP contacted by members of the group said he believed there were around a dozen MPs in his party close to quitting. Those involved in the organisation are understood to have conducted significant polling, including in target constituencies.

“I honestly believe this is imminent. You will see the values emphasised first, rather than policies to help people make that change. There are the names that are public but others are involved, including in the organisation of it, who have never been named,” the MP said.